2001 Cobra Problem (Overheating)

[20Snake01]

Hey guy got a little problem with overheating issues with my 2001 Cobra. My cobra has 94k miles and yesterday as I was driving back home )which is about 200 miles away right now) my car started to overheat. I drove about 10 miles on it overheating minimum b/c I didn't realize the gauge was on overheat until I looked over 5-10 minutes into the drive. Anyway I exited and took it to a shop after letting it cool. I have a pretty good knowledge for cars but not amazing so me and the mechanic put a pressure test first, car held great no leaks at all and we put a lot of pressure on it. Second we replaced the t-stat then started her up, at idle car did not overheat and seems fine staying right in the middle, so we tok it for a drive. While driving the car started to overheat again slowly after about 3-5 minutes. We took it back to the shop and just let the car idle with the Radieator cap off trying to let any air out of the system, we let it sit for about 10-15 min and car never overheated. We took to for another spin and again overheating. Engine is not showing any mixure of oil and coolant and also noticed that when I was driving and turned on the heat that it was blowing cold air and also noticed that before I took her on the road I turned on the air on and it was just blowing outside like tempertures. Im in Florida where right now its cold in the a.m. and a little warm in the p.m. which is why I had it on hot and cold.. Anyone have any suggestion? sorry for the long post, just trying to put all the info out there

 

[wmburns]

check water pump. Clean and flush.

Let's assume that the car is really overheating. I did work on a friend's car. Turned out to be a bad ground to the temperature guage. It said hot but in fact was not.

The usual list of things to check:
1. Thermostat (already done)
2. Pressure test (already done). Often overlooked.
3. Air in the system (often takes multiple heat/cool off cycles to purge. Especially in a DOHC).
4. Coolant problem (dirty, concentration too high/low, level too high/low).
5. Radiator clogged.
6. Fan not working. Check the fan shroud as well.
7. Water pump bearings. If the pump has excessive bearing play, this could reduce the pump’s output.
8. Internal engine problem such as head gasket failure, timing, blocked exhaust/cats.

The heater blowing cold air means there is air bubbles in the system. If the engine was already too hot, this is to be expected. If not, this is an important clue. Most likley the water pump is cavatating (bad bearings). Check the bearings in the pump for excessive play. Take the belt off and spin the pump. Look for too hard or up/down/in/out play in the pump shaft.

It has been my experience that when a car SLOWLY overheats, it is usually the T-stat, the fan not working, or the radiator is internally clogged or externally blocked.

Clean the radiator externally. Use a hose and clean from the front and back.

Next confirm the fan is running. Turn the AC on and verify the fan runs. Let idle until warm. You should hear the fan cycling on/off.

Next, flush the radiator with a chemical cleaner. Follow the instructions. If you get a lot of sediment out the lower radiator hose, consider removing/replacing the radiator. It is possible to have a radiator shop thoroughly clean. However, many people believe that for a stock radiator with plastic end caps, getting a new one makes more sense.

Note when refilling. The DOHC motor is very difficult to re-fill and get all of the air out. There are plenty of people out there that would say vacuum re-filling is the only real answer.

Let us know and we will go from there. Good luck.

 

[Kilgore Trout]

Its tricky to get the air out of the system so most likely you have air in there still.

Other problems could be cap not sealing or crack in expansion tank.

 

[COBRA90GT]

I bet you when the mechanic refilled the cooling system with coolant (after the t-stat change), he added coolant at the wrong location and now there is air trapped in the system.

I'm curious why the car was starting to overheat before the mechanic started messing with it though. Perhaps your t-stat was headed south.

On modular 4V engines, you need to add coolant at the coolant crossover plug location (remove the 1/4" plug located right by the alternator). You'll have to verify this first before you continue to troubleshoot your overheating problem.

Do you remember if the mechanic added coolant at the coolant crossover tube location or did he just pour it into the overflow container/catch system?


The correct way to refill a cobra cooling system is as follows:

Drain coolant, open coolant resevoir cap, open coolant crossover tube plug. Add coolant into coolant crossover tube location. Be very careful when removing the 1/4" plug here because too many people rush it and strip the square shaped plug - then you have to use vice grips and mangle up the plug or worse. One way to help loosen it, if it's never been removed before, is to run the engine for 5 minutes - the heat from the cooling system can help to "break" it loose.

Add coolant where you remove the 1/4" plug and continue to add coolant until the coolant rises to the top of the resevoir container, then put cap on the resevoir container. Start engine up, turn heat on full blast. Continue to add coolant at the coolant crossover tube location (1/4" plug) and once it is almost to the top of that location, slightly rev the engine by manipulating the throttle body with your hand. You'll see some air bubbles rise to the top. It may help to place a rag or two near the coolant crossover tube to catch any spills (using a funnel helps tremendously with keeping "splash" from leaking down below onto your garage floor). You'll want the car to come up to temperature (having an aftermarket water temp gauge helps a lot) so you can verify the t-stat is functional and to completely eliminate air in the cooling system. It may help to slightly jack up or raise the front end, but it's not really necessary as the coolant crossover tube location is the highest point in the cooling system. Seeing the air bubbles rise to the top and "gurgle" out is the procedure that everyone refers to as "burping."

Shut engine off, allow it to cool. Check coolant level at the resevoir (should stilll remain full) and if need be, add a little more coolant at the coolant crossover tube.

You may have to "burp" the cobra cooling system a couple of times to make sure all of the air has been purged out of the cooling system.


G'luck.

 

[twogts4us]

Yeah, I'm voting for air in the system as well.

 

[verucabri]

It was air in the system. thanks for all the advice. All is well.